1. Field of the Invention
The invention relates to a power-loom harness fitted with an upper and lower, sectionally contoured, rail, for instance a bar rail, hereafter called "rail", the heddles being held to the rails by means of eyes in their ends.
2. Description of the Related Art
Several harnesses of the initially cited kind form a so-called harness system. The individual harnesses of this system are alternately raised and lowered by means of a harness machine in accordance with predetermined patterns in order that sheds shall be formed from warp yarns guided by the heddles, a filling yarn being transported into the sheds. Conventionally the heddle eyes and the rails are so structured that, for one direction of motion of the harness, one of the rails rests by a drive surface against a mating heddle eye and drives these heddles. As regards the other direction of motion, the other rail by means of a drive surface drives a mating surface of the heddle eyes associated with it. Because the heddles and also the harness expand thermally and both are subject to certain manufacturing tolerances, and because the heddles must furthermore be displaceable along the rails, for instance to allow insertion or repair of the warps, the heddles are provided with a play of on the order of 2 to 3 mm between the drive surface of one rail and the drive surface of the other rail.
When the harness is in the raised position, the heddles, that is their eyes, make contact with the drive surface of the upper rail. If thereupon the harness is lowered, the heddles disengage, due to tension in the warps and inertia, at a given time, from the drive surface of the upper rail and thereafter make contact with the drive surface of the lower rail. Similarly, the heddles disengage, at a given time during the upward motion of the harness, from the drive surface of the lower rail and thereafter make contact with the drive surface of the upper rail. The disengagement of the heddles from one rail and their subsequent application against the other rail following a free displacement in the direction of motion of the harness over a path of 2-3 mm causes impacts which entail noise on one hand and heddle vibration on the other hand. Especially at high speeds and in the long term, these impacts and the vibrations so incurred may cause rupture of the heddles and/or of the harnesses.
It is known from the German patent document U 94 13 705.6 to use only one rail as the drive rail to drive the heddles both during the raising and the lowering of the harness, so that the play may be reduced and the magnitude of the impacts may be lessened. In the known design, the rail acting as the drive rail is accordingly fitted with a thin, transverse leg that enters, with little play, a drive slot of the associated eye of the heddles.